We’re talking about an extraordinarily inexpensive material, light enough to protect satellites from debris in the cold of space, cohesive enough to strengthen the walls of pressure vessels exposed to average Earth conditions, yet heat-resistant enough at 1,500 Protecting instruments from flying debris at 2,732 degrees Celsius, or 2,732 degrees Fahrenheit, begs the question: What single material could do all of this? The answer, found at Sandia National Laboratories, is sweet as candy.
That’s because it’s actually sugar — very thin layers of grocery store powdered sugar, baked to a state called soot, interspersed between only slightly thicker layers of silicon dioxide, the most common material on earth, and baked. The result resembles a fine layered cake, or more specifically, the organic and inorganic layering of a seashell, with each layer helping the next to contain and mitigate shocks.
“A material that can survive a variety of stresses — mechanical, shock and X-rays — can be used to withstand harsh environmental conditions,” said Sandia researcher Guangping Xu, who led the development of the new coating. “This material was not readily available. We believe our layered nanocomposite, which mimics the structure of a seashell, is the answer.”
Most importantly, Xu said, “The self-assembled coating is not only lightweight and mechanically strong, but also thermally stable enough to protect instruments in experimental fusion machines from their own generated debris, where temperatures can reach around 1,500C.” This was the original focus of the work.”
“And this could just be the beginning,” said consultant Rick Spielman, senior scientist and physics professor at the University of Rochester’s Laboratory for Laser Energetics, who is credited with leading the initial design of Sandia’s Z-Machine, one of the goals for the the new material is planned. “There are probably a hundred uses that we haven’t thought of.” He envisions potential electrode applications that delay rather than block surface electron emissions. Support nuclear survival mission
The coating, which can be applied to a variety of substrates without environmental concerns, was the subject of a Sandia patent application in June 2021, an invited talk at a Pulsed Power conference in December 2021, and again in a recent paper in MRS advanceswhose main author is Xu.
The work was conducted in anticipation of the increased shielding that will be required to protect test objects, diagnostics and drivers in the more powerful pulsed prime movers of the future. Sandia’s Pulsed Z-Machine – currently the most powerful X-ray generator on Earth – and its successors will certainly need even greater debris protection against forces that might compare to numerous sticks of dynamite detonating at close range. Chad McCoy loads sample coatings onto Sandia’s Z machine
Physicist Chad McCoy at Sandia National Laboratories’ Z-Machine loads sample coatings into holders. When Z fires, researchers will observe how well certain coatings protect objects stacked behind it. (Photo by Bret Latter) Click on thumbnail for high resolution image.
“The new shield should have a positive impact on our nuclear survivability mission,” said study author and Sandia physicist Chad McCoy. “Z is the brightest X-ray source in the world, but the amount of X-rays is only a few percent of the total energy released. The rest is tremors and debris. When we try to understand how matter – like metals and polymers – interacts with X-rays, we want to know if debris has damaged our samples, altered their microstructure. At the moment we are at the limit of where we can protect specimens from unwanted attacks, but more powerful testing machines will require better shielding and this new technology may provide adequate protection.”
Other less specialized uses remain possible.
The low-cost, eco-friendly shield is light enough to fly into space as a protective layer on satellites, as comparatively little material is needed to achieve the same toughness as heavier but less effective shields currently used to protect against space debris collisions . “Satellites in space are constantly being hit by debris moving at a few kilometers per second, the same speed as debris from Z,” McCoy said. “With this coating, we can make the dirt shield thinner and lighten the weight.”
Thicker shielding coatings are durable enough to reinforce pressure vessel walls when extra ounces are not a problem. Drastic cost reduction expected
The material cost to produce a coating of the new protective material, 2 inches in diameter and 45 millionths of a meter and microns thick, is only 25 cents, according to Guangping. In contrast, a beryllium wafer – which comes closest to the thermal and mechanical properties of the new coating and is used as protective shields in Sandia’s Z-Machine and other fusion sites – costs $700 for a 1-inch square at current market prices, 23 micron thick wafer, which is 3,800 times more expensive than the new film of the same area and thickness.
Both coatings can withstand temperatures well in excess of 1,000C, but an additional consideration is that the new coating is environmentally friendly. Only ethanol is added to facilitate the coating process. Beryllium creates toxic conditions, and its environment must be cleansed of the hazard after its use. How the exam went
The principle of alternating organic and inorganic layers, an important factor in shellfish longevity, is key to strengthening the Sandia coating. The organic sugar layers burned into soot act like a caulk, said Sandia manager and paper author Hongyou Fan. They also prevent cracks from propagating through the inorganic silica structure and provide cushion layers to increase mechanical strength, like 20 years ago in one earlier attempt by Sandia to emulate shell mode.
Greg Frye-Mason, Sandia campaign manager for the Assured Survivability and Agility with Pulsed Power, or ASAP, Laboratory Directed Research and Development mission campaign that funds the research, initially had doubts about the carbon insertion.
“I thought the organic layers would limit its applicability since most degrade at 400-500°C,” he said.
But when the soot concept demonstrated robustness well in excess of 1,000°C, the positive result overcame the greatest risk Frye-Mason saw in the project.
Shell-like coatings originally tested at Sandia varied from a few to 13 coats. After being heated in pairs, these alternating materials were pressed against one another, causing their surfaces to crosslink. Tests showed that such interwoven nanocomposite layers of silicon dioxide with the burnt sugar, known as soot after pyrolysis, are 80% stronger than silicon dioxide itself and thermally stable up to an estimated temperature of 1,650 °C -coating processes, could be batch baked and their individual Surfaces were still satisfactorily cross-linked, eliminating the tedious task of baking each coat. The more efficient process achieved almost the same mechanical strength.
Research on the coating was funded by ASAP to develop methods to protect diagnostic and test samples on Z and next-generation pulsed engines from flying debris.
“This coating is suitable,” said Frye-Mason.